Eur. J. Epidemiol. 0392-2990
EUROPEAN
September 1992, p. 730-732
Vol. 8, No. 5
JOURNAL
Or
EPIDEMIOLOGY
PROXIMAL FEMORALFRACTURES: PREVALENCE IN DIFFERENT RACIAL GROUPS M. PARKER*, J.K. ANAND *.1, J.W. MYLES*** and R. LODWICK**** *Peterborough District Hospital- Peterborough - PE 36 DA - England. **68 Ledbury R o a d - Peterborough - PE 39 P J - England. **'17 Audley Gate - Peterborough - PE 39 PG - England. ****Sandwell District Hospital- West Bromwich West Midlands - B 71 4HJ- England. From the Hip Fracture Project Peterborough District Hospital and the Birmingham Accident Hospital
Key words: Proximal femoral fractures - Race - Genetic - Osteoporosis - Methodology This paper describes the methodology and the results of a study performed in Central England.
The predominant racial group here is "White European" (Europid). There are smaller numbers of people of Indian origin (Indids) and still smaller numbers of Afro-Caribbean and of Mongolian ancestry (Mongoloids). We found no significant differences in the incidence of hip fractures in the first two groups. The study population was 1600 consecutive patients with proximal femoral fractures (PFF). The difficulties of racial classification are discussed. To elucidate the predisposing factors for PFF, large scale collaborative studies between medical centres in the major European, Asian, African and American conurbations are suggested. Racial burden may be one such factor; osteoporosis may be another.
INTRODUCTION
Our aim was two-fold - firstly, to construct a methodology for a comparative study of the prevalence o f proximal femoral fractures (PFF) in the four main racial groups in England and secondly, to study the racial differences in the prevalence. According to Gypes, Mellins, and Katz (5), Riggs and Melton (11) and Solomon (13) Negroes have a very low incidence o f hip fractures. In Singapore Wong (14) found that hip fractures were commoner in people o f Indian origin than in those of Chinese or Malay descent. Classification o f the human race is bedevilled by confusion in definition and political attitudes. For simplicity we have aggregated the people originating from India, Pakistan, Bangladesh, and Sri Lanka as Indids, those o f European origin as Europids, those originating from China, Hong Kong and Indo-China as Mongoloid and those o f African or 1 Corresponding author.
730
West Indian descent as Afro-Caribbeans. We recognise that there is an element of overlap between all these divisions. Our methodology is appficable to the population we studied - 1600 patients who could, we hoped, be classified in to the four divisions (Europids, Indids, Mongoloids and Afro-Caribbeans). This is the first published report on this subject, from Europe. The overall average age of patients was 79 years. The average age in the intracapsular group being 78 years and in the extracapsular group, 80 years. Whereas 17% of the intracapsular fractures occurred in males and 83% in females, in the extracapsular group, 19% o f patients were male and 81% female. Intracapsular fractures comprised 51% of the total and the extracapsular 49%. Patients and methods
a) - D e f i n i t i o n o f cases. Clinical diagnosis o f proximal femoral fracture was supplemented by radiography. On this basis the patients were individually assigned
Vol. 8, 1992
Racial risk factors for proximal femoral fractures
either to the intracapsular or the extracapsular groups. Elsewhere we have described the presenting characteristics of intracapsular and extracapsular fractures. (The numbers of racial minorities in the two groups were too small for a reliable statistical study of racial differences). b) - Assigning a patient to a racial group. One of us (MP) visually determined the racial origins of 770 consecutive patients treated for PFF at the Birmingham accident Hospital and Peterborough District Hospital. In addition, using the method of Raleigh (10), the names of a further 830 patients with PFF were studied by JKA to ascertain the presumptive race. In England, migrants from the Indian subcontinent (Indids), are mostly Hindus, Moslems or Sikhs. Their names are characteristic of their religion as has been previously described by Anand (2). Where a doubt arose, as is the case with mixed European and Eastern sounding forenames and sumames, a study of the case-notes including the diet-sheet resolved the matter. The Raleigh method cannot be used for an Afro-Caribbean population in England as these individuals have very largely European sounding names, reflecting the dominance of Christian religion amongst them. In the case of the Mongoloid subjects in England, Anglicisation of the name is uncommon and the patient's full name is a good indicator of the racial origin in the age band in which we are studying hip fractures. c) - Estimating the population at risk for the different racial groups. The "at risk" population with an average age similar to that for the patients with PFF was estimated from population data, based on the 1981 census and the 1981 Labour Force Study (9). The estimate was evaluated by analysing the forenames and surnames of 3000 acute geriatric ward patients to assess their presumed racial origin. Of the 770 patients personally seen, 768 (99.7%) were Europid and 2 (0.3%) Indid. There were no Afro-Caribbean or Mongoloid patients with hip fractures in this series. Out of the 830 patients whose names were studied, 5 (0.6O/o) were of presumed Indid origin. Using the 1981 census details of the place of birth of residents within the catchment areas of the hospitals concerned, we were able to estimate the population of different racial origins. Europids (described in the census as Caucasians) were 97.1°/0, Indids (Asians in the census terminology) 1.4, Afro-Caribbeans 1.20/0, Mongoloids 0.3%. From the 1981 Labour Force Survey we found that 18% of the people were over the age of retirement and were Europid, 2% were Afro-Caribbean, 3% were Indid and 3% were Mongoloid. Using these figures, we estimated that the proportion of the different racial groups over the age of 65 is as follows: Europids 99.4%, Indids 0.30/0, Mongoloid 0.1% and Afro-Caribs 0.2%. d) - Period of study and demographic stability. The patient statistics were collected between October 1986
and July 1991. The study population covered all the local patients except those who sustained a fracture whilst away from their home district and it also included those who might have been visiting the area. With 223 cases of PFF in the Peterborough hospitals from a catchment of 280000, the annual rate works out at 80 per 100000 population. No major changes in the catchment population mix are known to have occurred during the study period. Information concerning the place of birth was not collected. RESULTS
Table I shows the numbers of cases of PFF which would be expected on purely statistical grounds in relation to the total numbers in the population in each racial group and contrasts these "theoretical cases" with the patients in each group who were actually encountered. It is apparent that while the Europids and the Indids correlate well between the numbers expected and those actually encountered, this is not the case with the Afro-Caribbeans and the Mongoloids. Our results in this respect arre broadly in line with those obtained by other authors. TABLE 1. - Observed and expected numbers (and percentages) of hip fractures in different racial groups. Europids
Indids
Afro-Caribbeans
Mongoloids
Observed 1593 (99.6)
7 (0.4)
0
0
Expected 1590 (99.4)
5 (0.3)
3 (0.2)
2 (0.1)
DISCUSSION
Most of the published work on the relative racial incidence of PFF has been carried out in the United States on Europids and American blacks - who are largely of Afro-Caribbean descent though often with Europid admixture. The contribution of Amerindian genes to the present day population of the United States is impossible to quantify. The Amerindians are of Mongoloid ancestory. The incidence of PFF reported from different countries varies widely. Makin (7), in his series of 378 Western and 230 Eastern (but non-Israeli) women with PFF found that in Jerusalem the Jewish inhabitants of European origin had a slightly higher rate of fractures. There was no correlation with the prevalence of osteoporosis in the community. From Singapore, Wong (14) reported a higher incidence in those of Indian origin than in the Chinese and the Malays. (He excluded the small numbers of Europeans and Eurasians from his study). Solomon (B) in Johannesburg found that the Bantu had one tenth the rate of PFF as compared with the Whites. Although he does not give comparable local figures for non-Africans, Adebajo from Ibadan asserts (1)
731
Parker M. et al.
Eur. J. Epidemiol.
that in his West African City, there were only 11 cases of hip fracture in a population of one million. In Texas, analysing the data for 576 residents with hip fractures not due to severe trauma, Bauer (4) recorded a reduced risk in Mexican Americans and blacks. Silverman and Madison (12) from California reported lower risk for hip fracture in Hispanic, Black, and Asian American females than in White females who were not Hispanic. White non-Hispanic males had the highest incidence among men. Kellie and Brodie (6) studied the Medicare-reimbursed hip fractures hospitalised from 1980 to 1982. They found the highest rates in White women, lowest in Black men, and intermediate rates in White men and Black women. From the foregoing it appears that on the whole, African ancestry has a protective influence, and in this regard, Hispanic genes too are beneficial. Indid heritage shows a greater vulnerability than the Chinese or the Malay, in Singapore. In Jerusalem, Oriental or African ancestry is slightly protective. Our study indicates that the Indids in England are no less vulnerable to PFF than are the Europids, but the numbers are too small for firm conclusions to be drawn. We have demonstrated that our methodology can be applied in populations which retain their traditional culture. It is applicable therefore to Indids and Mongoloids in Europe, Singapore, Africa and the North American Continent. The analysis of the 1991 census should enable large scale studies using our methodology to attain reliable results. It should be pointed out that similar methods have been used by Nicoll, Bassett and Ulijaszek (8) in their epidemiological work. There is clearly a need for developing an anthropological classification and methodology which can be applied universally to study the relationship between race and disease - in so far and so long as racial identity is definable. In England, racial classification is inevitably an exercise in compromise. The Celts, the Belgae, the Mediterranid and Mediterranid / Beaker Folk hybrids, the Anglo-Saxons, the Vikings and the Normans were derived from the Europid branch of the Caucasoid sub-race. They, with some admixture of later arrivals comprise the "whites" of England. The Indids in our studies are derived very largely, from the Indo-Afghans a people inhabiting the Indo-Gangetic basin. The Bangladeshis, coming from the area just west of Burma may have some Mongoloid admixture to a largely IndoAfghan branch of the Caucasoid sub-race. The Indus Valley archaeology has yielded skeletons identified by Sewell and Guha, [cited by Baker (3)] as Mediterranid, another branch of the Caucasians. We must point out that the Mongoloids comprise a much greater proportion of the world population than the Indids and the Europids as defined here. The genetic diversity amongst the Mongoloids must, therefore, be substantial. A study of the racial incidence of fractures is merely the beginning. We believe the true epidemiology of osteoporosis and bone fragility is largely related to genetic determinants of enzymatic characteristics which may run through certain families, though of course there must be considerable interplay of these with environmental and life style factors.
In this series of proximal femoral fractures our methodology of determining comparative racial incidence proved suitable for the Indids and the Europids. The absence of statistically significant difference between the two populations is noteworthy. The studies need to be repeated in other, larger populations, using comparable definitions and methodology. To dissect out the relative contributions of genetic, dietetic and environmental factors, uniformity of terminology is important. Agreed anthropological classification is crucial.
732
REFERENCES
1. Adejabo A.O. (1989): Dietary calcium, physical activity and risk of hip fracture - Brit. Med. J. 299: 1165. 2. Anand J.K. (1968): On name dropping and name tracking - The Medical Officer, CXIX 12: 160-161. 3. Baker J.R. (1974): Race. London: Oxford University Press. 4. Bauer R.L. (1988): Ethnic differences in hip fracture: a reduced incidence in Mexican Americans - Amer. J. Epidem. 127(1): 145-149. 5.
Gyepes M., Mellins tI.Z. and Katz L (1962): The low incidence of fracture of the hip in the negro - JAMA 181: 1073-1074.
6. Kellie S.E. and Brody J.A. (1990): Sex specific and race specific hip fracture rates - Amer. J. Pub. Health 80 (3): 326-328. 7. Makin M. (1987): Osteoporosis and proximal femoral fractures in the female elderly in Jemsaleda - Clin. Orthop. and related research 218: 19-23. 8. Nieoll A., Bassett K. and Ulijasek S.J. (1986): What's in a name? Accuracy of using surnames and forenames in ascribing Asian identity in English populations - J. Epidem. and Community Health 40: 364-368. 9.
Office of Population Censuses and Surveys. Labour Force Study 1981: country of birth and ethnic origin London: HMSO, 1983.
10. Raleigh V.S., Bulusu L. and Balarajan R. (1990): Suicides among immigrants from the Indian subcontinent - Br. J. Psych. 156: 46-50. 11. Riggs B.L. and Melton L.J. (1988): Osteoporosis: etiology, diagnosis and management - New York: Raven Press. 12. Silverman S.L. and Madison R.E. (1988): Decreased incidence of hip fracture in Hispanics, Asians and blacks - Amer. J. Pub. Health 78 (11): 1482-1483. 13. Solomon L. (1979): Bone density in ageing Caucasian and African populations - The Lancet 2: 1326-1330. 14. Wong P.C.N. (1964): Femoral neck fractures among the major racial groups in Singapore: incidence patterns compared with non Asian communities Singapore Med. J. 5: 150-157.
EUROPEAN
September 1992, p. 730-732
Vol. 8, No. 5
JOURNAL
Or
EPIDEMIOLOGY
PROXIMAL FEMORALFRACTURES: PREVALENCE IN DIFFERENT RACIAL GROUPS M. PARKER*, J.K. ANAND *.1, J.W. MYLES*** and R. LODWICK**** *Peterborough District Hospital- Peterborough - PE 36 DA - England. **68 Ledbury R o a d - Peterborough - PE 39 P J - England. **'17 Audley Gate - Peterborough - PE 39 PG - England. ****Sandwell District Hospital- West Bromwich West Midlands - B 71 4HJ- England. From the Hip Fracture Project Peterborough District Hospital and the Birmingham Accident Hospital
Key words: Proximal femoral fractures - Race - Genetic - Osteoporosis - Methodology This paper describes the methodology and the results of a study performed in Central England.
The predominant racial group here is "White European" (Europid). There are smaller numbers of people of Indian origin (Indids) and still smaller numbers of Afro-Caribbean and of Mongolian ancestry (Mongoloids). We found no significant differences in the incidence of hip fractures in the first two groups. The study population was 1600 consecutive patients with proximal femoral fractures (PFF). The difficulties of racial classification are discussed. To elucidate the predisposing factors for PFF, large scale collaborative studies between medical centres in the major European, Asian, African and American conurbations are suggested. Racial burden may be one such factor; osteoporosis may be another.
INTRODUCTION
Our aim was two-fold - firstly, to construct a methodology for a comparative study of the prevalence o f proximal femoral fractures (PFF) in the four main racial groups in England and secondly, to study the racial differences in the prevalence. According to Gypes, Mellins, and Katz (5), Riggs and Melton (11) and Solomon (13) Negroes have a very low incidence o f hip fractures. In Singapore Wong (14) found that hip fractures were commoner in people o f Indian origin than in those of Chinese or Malay descent. Classification o f the human race is bedevilled by confusion in definition and political attitudes. For simplicity we have aggregated the people originating from India, Pakistan, Bangladesh, and Sri Lanka as Indids, those o f European origin as Europids, those originating from China, Hong Kong and Indo-China as Mongoloid and those o f African or 1 Corresponding author.
730
West Indian descent as Afro-Caribbeans. We recognise that there is an element of overlap between all these divisions. Our methodology is appficable to the population we studied - 1600 patients who could, we hoped, be classified in to the four divisions (Europids, Indids, Mongoloids and Afro-Caribbeans). This is the first published report on this subject, from Europe. The overall average age of patients was 79 years. The average age in the intracapsular group being 78 years and in the extracapsular group, 80 years. Whereas 17% of the intracapsular fractures occurred in males and 83% in females, in the extracapsular group, 19% o f patients were male and 81% female. Intracapsular fractures comprised 51% of the total and the extracapsular 49%. Patients and methods
a) - D e f i n i t i o n o f cases. Clinical diagnosis o f proximal femoral fracture was supplemented by radiography. On this basis the patients were individually assigned
Vol. 8, 1992
Racial risk factors for proximal femoral fractures
either to the intracapsular or the extracapsular groups. Elsewhere we have described the presenting characteristics of intracapsular and extracapsular fractures. (The numbers of racial minorities in the two groups were too small for a reliable statistical study of racial differences). b) - Assigning a patient to a racial group. One of us (MP) visually determined the racial origins of 770 consecutive patients treated for PFF at the Birmingham accident Hospital and Peterborough District Hospital. In addition, using the method of Raleigh (10), the names of a further 830 patients with PFF were studied by JKA to ascertain the presumptive race. In England, migrants from the Indian subcontinent (Indids), are mostly Hindus, Moslems or Sikhs. Their names are characteristic of their religion as has been previously described by Anand (2). Where a doubt arose, as is the case with mixed European and Eastern sounding forenames and sumames, a study of the case-notes including the diet-sheet resolved the matter. The Raleigh method cannot be used for an Afro-Caribbean population in England as these individuals have very largely European sounding names, reflecting the dominance of Christian religion amongst them. In the case of the Mongoloid subjects in England, Anglicisation of the name is uncommon and the patient's full name is a good indicator of the racial origin in the age band in which we are studying hip fractures. c) - Estimating the population at risk for the different racial groups. The "at risk" population with an average age similar to that for the patients with PFF was estimated from population data, based on the 1981 census and the 1981 Labour Force Study (9). The estimate was evaluated by analysing the forenames and surnames of 3000 acute geriatric ward patients to assess their presumed racial origin. Of the 770 patients personally seen, 768 (99.7%) were Europid and 2 (0.3%) Indid. There were no Afro-Caribbean or Mongoloid patients with hip fractures in this series. Out of the 830 patients whose names were studied, 5 (0.6O/o) were of presumed Indid origin. Using the 1981 census details of the place of birth of residents within the catchment areas of the hospitals concerned, we were able to estimate the population of different racial origins. Europids (described in the census as Caucasians) were 97.1°/0, Indids (Asians in the census terminology) 1.4, Afro-Caribbeans 1.20/0, Mongoloids 0.3%. From the 1981 Labour Force Survey we found that 18% of the people were over the age of retirement and were Europid, 2% were Afro-Caribbean, 3% were Indid and 3% were Mongoloid. Using these figures, we estimated that the proportion of the different racial groups over the age of 65 is as follows: Europids 99.4%, Indids 0.30/0, Mongoloid 0.1% and Afro-Caribs 0.2%. d) - Period of study and demographic stability. The patient statistics were collected between October 1986
and July 1991. The study population covered all the local patients except those who sustained a fracture whilst away from their home district and it also included those who might have been visiting the area. With 223 cases of PFF in the Peterborough hospitals from a catchment of 280000, the annual rate works out at 80 per 100000 population. No major changes in the catchment population mix are known to have occurred during the study period. Information concerning the place of birth was not collected. RESULTS
Table I shows the numbers of cases of PFF which would be expected on purely statistical grounds in relation to the total numbers in the population in each racial group and contrasts these "theoretical cases" with the patients in each group who were actually encountered. It is apparent that while the Europids and the Indids correlate well between the numbers expected and those actually encountered, this is not the case with the Afro-Caribbeans and the Mongoloids. Our results in this respect arre broadly in line with those obtained by other authors. TABLE 1. - Observed and expected numbers (and percentages) of hip fractures in different racial groups. Europids
Indids
Afro-Caribbeans
Mongoloids
Observed 1593 (99.6)
7 (0.4)
0
0
Expected 1590 (99.4)
5 (0.3)
3 (0.2)
2 (0.1)
DISCUSSION
Most of the published work on the relative racial incidence of PFF has been carried out in the United States on Europids and American blacks - who are largely of Afro-Caribbean descent though often with Europid admixture. The contribution of Amerindian genes to the present day population of the United States is impossible to quantify. The Amerindians are of Mongoloid ancestory. The incidence of PFF reported from different countries varies widely. Makin (7), in his series of 378 Western and 230 Eastern (but non-Israeli) women with PFF found that in Jerusalem the Jewish inhabitants of European origin had a slightly higher rate of fractures. There was no correlation with the prevalence of osteoporosis in the community. From Singapore, Wong (14) reported a higher incidence in those of Indian origin than in the Chinese and the Malays. (He excluded the small numbers of Europeans and Eurasians from his study). Solomon (B) in Johannesburg found that the Bantu had one tenth the rate of PFF as compared with the Whites. Although he does not give comparable local figures for non-Africans, Adebajo from Ibadan asserts (1)
731
Parker M. et al.
Eur. J. Epidemiol.
that in his West African City, there were only 11 cases of hip fracture in a population of one million. In Texas, analysing the data for 576 residents with hip fractures not due to severe trauma, Bauer (4) recorded a reduced risk in Mexican Americans and blacks. Silverman and Madison (12) from California reported lower risk for hip fracture in Hispanic, Black, and Asian American females than in White females who were not Hispanic. White non-Hispanic males had the highest incidence among men. Kellie and Brodie (6) studied the Medicare-reimbursed hip fractures hospitalised from 1980 to 1982. They found the highest rates in White women, lowest in Black men, and intermediate rates in White men and Black women. From the foregoing it appears that on the whole, African ancestry has a protective influence, and in this regard, Hispanic genes too are beneficial. Indid heritage shows a greater vulnerability than the Chinese or the Malay, in Singapore. In Jerusalem, Oriental or African ancestry is slightly protective. Our study indicates that the Indids in England are no less vulnerable to PFF than are the Europids, but the numbers are too small for firm conclusions to be drawn. We have demonstrated that our methodology can be applied in populations which retain their traditional culture. It is applicable therefore to Indids and Mongoloids in Europe, Singapore, Africa and the North American Continent. The analysis of the 1991 census should enable large scale studies using our methodology to attain reliable results. It should be pointed out that similar methods have been used by Nicoll, Bassett and Ulijaszek (8) in their epidemiological work. There is clearly a need for developing an anthropological classification and methodology which can be applied universally to study the relationship between race and disease - in so far and so long as racial identity is definable. In England, racial classification is inevitably an exercise in compromise. The Celts, the Belgae, the Mediterranid and Mediterranid / Beaker Folk hybrids, the Anglo-Saxons, the Vikings and the Normans were derived from the Europid branch of the Caucasoid sub-race. They, with some admixture of later arrivals comprise the "whites" of England. The Indids in our studies are derived very largely, from the Indo-Afghans a people inhabiting the Indo-Gangetic basin. The Bangladeshis, coming from the area just west of Burma may have some Mongoloid admixture to a largely IndoAfghan branch of the Caucasoid sub-race. The Indus Valley archaeology has yielded skeletons identified by Sewell and Guha, [cited by Baker (3)] as Mediterranid, another branch of the Caucasians. We must point out that the Mongoloids comprise a much greater proportion of the world population than the Indids and the Europids as defined here. The genetic diversity amongst the Mongoloids must, therefore, be substantial. A study of the racial incidence of fractures is merely the beginning. We believe the true epidemiology of osteoporosis and bone fragility is largely related to genetic determinants of enzymatic characteristics which may run through certain families, though of course there must be considerable interplay of these with environmental and life style factors.
In this series of proximal femoral fractures our methodology of determining comparative racial incidence proved suitable for the Indids and the Europids. The absence of statistically significant difference between the two populations is noteworthy. The studies need to be repeated in other, larger populations, using comparable definitions and methodology. To dissect out the relative contributions of genetic, dietetic and environmental factors, uniformity of terminology is important. Agreed anthropological classification is crucial.
732
REFERENCES
1. Adejabo A.O. (1989): Dietary calcium, physical activity and risk of hip fracture - Brit. Med. J. 299: 1165. 2. Anand J.K. (1968): On name dropping and name tracking - The Medical Officer, CXIX 12: 160-161. 3. Baker J.R. (1974): Race. London: Oxford University Press. 4. Bauer R.L. (1988): Ethnic differences in hip fracture: a reduced incidence in Mexican Americans - Amer. J. Epidem. 127(1): 145-149. 5.
Gyepes M., Mellins tI.Z. and Katz L (1962): The low incidence of fracture of the hip in the negro - JAMA 181: 1073-1074.
6. Kellie S.E. and Brody J.A. (1990): Sex specific and race specific hip fracture rates - Amer. J. Pub. Health 80 (3): 326-328. 7. Makin M. (1987): Osteoporosis and proximal femoral fractures in the female elderly in Jemsaleda - Clin. Orthop. and related research 218: 19-23. 8. Nieoll A., Bassett K. and Ulijasek S.J. (1986): What's in a name? Accuracy of using surnames and forenames in ascribing Asian identity in English populations - J. Epidem. and Community Health 40: 364-368. 9.
Office of Population Censuses and Surveys. Labour Force Study 1981: country of birth and ethnic origin London: HMSO, 1983.
10. Raleigh V.S., Bulusu L. and Balarajan R. (1990): Suicides among immigrants from the Indian subcontinent - Br. J. Psych. 156: 46-50. 11. Riggs B.L. and Melton L.J. (1988): Osteoporosis: etiology, diagnosis and management - New York: Raven Press. 12. Silverman S.L. and Madison R.E. (1988): Decreased incidence of hip fracture in Hispanics, Asians and blacks - Amer. J. Pub. Health 78 (11): 1482-1483. 13. Solomon L. (1979): Bone density in ageing Caucasian and African populations - The Lancet 2: 1326-1330. 14. Wong P.C.N. (1964): Femoral neck fractures among the major racial groups in Singapore: incidence patterns compared with non Asian communities Singapore Med. J. 5: 150-157.
